LINER LTC3225

LTC3225
150mA Supercapacitor
Charger
FEATURES
DESCRIPTION
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The LTC®3225 is a programmable supercapacitor charger
designed to charge two supercapacitors in series to a
fixed output voltage (4.8V/5.3V selectable) from a 2.8V/3V
to 5.5V input supply. Automatic cell balancing prevents
overvoltage damage to either supercapacitor. No balancing
resistors are required.
n
n
n
n
n
n
n
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Low Noise Constant Frequency Charging of Two
Series Supercapacitors
Automatic Cell Balancing Prevents Capacitor
Overvoltage During Charging
Programmable Charging Current (Up to 150mA)
Selectable 2.4V or 2.65V Regulation per Cell
Automatic Recharge
IVIN = 20μA in Standby Mode
ICOUT < 1μA When Input Supply is Removed
No Inductors
Tiny Application Circuit (3mm × 2mm DFN Package,
All Components <1mm High)
APPLICATIONS
n
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Current Limited Applications with High Peak Power
Loads (LED Flash, PCMCIA Tx Bursts, HDD Bursts,
GPRS/GSM Transmitter)
Backup Supplies
Low input noise, low quiescent current and low external
parts count (one flying capacitor, one bypass capacitor
at VIN and one programming resistor) make the LTC3225
ideally suited for small battery-powered applications.
Charging current level is programmed with an external
resistor. When the input supply is removed, the LTC3225
automatically enters a low current state, drawing less than
1μA from the supercapacitors.
The LTC3225 is available in a 10-lead 3mm × 2mm DFN
package.
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
Charging Profile with 30% Mismatch
in Output Capacitance, CTOP < CBOT
VIN
2.8V/3V TO 5.5V
VIN
COUT
0.6F
2.2μF
VOUT
4.8V/5.3V
C+
1μF
ON/OFF
OUTPUT
PROGRAMMING
CX
LTC3225
C–
GND
SHDN
PGOOD
SHDN
5V/DIV
IVIN
300mA/DIV
0.6F
100k
VCOUT
2V/DIV
VSEL
PROG
12k
3225 TA01a
VTOP-VBOT
200mV/DIV
5s/DIV
VSEL = VIN
RPROG = 12k
CTOP = 1.1F
CBOT = 1.43F
CTOP INITIAL VOLTAGE = 0V
CBOT INITIAL VOLTAGE = 0V
3225 TA01b
3225f
1
LTC3225
ABSOLUTE MAXIMUM RATINGS
(Note 1)
PIN CONFIGURATION
VIN, COUT to GND ......................................... –0.3V to 6V
SHDN, VSEL ...................................... –0.3V to VIN + 0.3V
COUT Short-Circuit Duration ............................. Indefinite
IVIN Continuous (Note 2) ......................................350mA
IOUT Continuous (Note 2) .....................................175mA
Operating Temperature Range (Note 3).... –40°C to 85°C
Storage Temperature Range................... –65°C to 125°C
TOP VIEW
C+ 1
10 COUT
C– 2
9
VIN
8
GND
SHDN 4
7
PROG
PGOOD 5
6
VSEL
CX 3
11
DDB PACKAGE
10-LEAD (3mm s 2mm) PLASTIC DFN
TJMAX = 125°C, θJA = 76°C/W
EXPOSED PAD (PIN 11) MUST BE SOLDERED TO
LOW IMPEDANCE GND PLANE (PIN 8) ON PCB
ORDER INFORMATION
Lead Free Finish
TAPE AND REEL (MINI)
TAPE AND REEL
PART MARKING
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LTC3225EDDB#TRMPBF
LTC3225EDDB#TRPBF
LCYR
10-Lead (3mm × 2mm) Plastic DFN
TRM = 500 pieces.
Consult LTC Marketing for parts specified with wider operating temperature ranges.
Consult LTC Marketing for information on lead based finish parts.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/
–40°C to 85°C
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = 3.6V, CIN = 2.2μF, CFLY = 1μF, unless otherwise specified.
SYMBOL
PARAMETER
CONDITIONS
VIN-UVLO
Input Supply Undervoltage Lockout
High-to-Low Threshold
VSEL = VIN
VSEL = 0
VIN-UVLO-HYS
Input Supply Undervoltage Lockout
Hysteresis
VSEL = VIN
VSEL = 0
VIN
Input Voltage Range
VSEL = VIN
VSEL = 0V
l
l
3
2.8
VCOUT
Charge Termination Voltage
Sleep Mode Threshold (Rising Edge)
VSEL = VIN
VSEL = 0V
l
l
5.2
4.7
l
l
MIN
TYP
MAX
UNITS
2.65
2.4
2.75
2.5
2.85
2.6
V
V
150
140
5.3
4.8
mV
mV
5.5
5.5
V
V
5.4
4.9
V
V
VCOUT-HYS
Output Comparator Hysteresis
VTOP/BOT
Maximum Voltage Across Each of the
Supercapacitors After Charging
VSEL = VIN
VSEL = 0V
l
l
100
mV
IQ-VIN
No Load Operating Current at VIN
IOUT = 0mA
l
20
40
μA
ISHDN-VIN
Shutdown Current
SHDN = 0V, VOUT = 0V
l
0.1
1
μA
ICOUT
COUT Leakage Current
VOUT = 5.6V, SHDN = 0V
VOUT = 5.6V, Charge Pump in Sleep Mode
VOUT = 5.6V, SHDN Connected to VIN with
Input Supply Removed
l
l
1
2
3
4
1
μA
μA
μA
IVIN
Input Charging Current
VIN = 3.6V, RPROG = 12k, CTOP = CBOT
306
mA
VIN = 3.6V, RPROG = 60k, CTOP = CBOT
55
mA
2.75
2.5
V
V
3225f
2
LTC3225
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = 3.6V, CIN = 2.2μF, CFLY = 1μF, unless otherwise specified.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
IOUT
Output Charging Current
VIN = 3.6V, RPROG = 12k, VOUT = 4.5V,
CTOP = CBOT
125
150
175
mA
VIN = 3.6V, RPROG = 60k, VOUT = 4.5V,
CTOP = CBOT
26
mA
VPGOOD
PGOOD Low Output Voltage
IPGOOD = –1.6mA
l
0.4
V
IPGOOD-LEAK
PGOOD High Impedance Leakage Current
VPGOOD = 5V
l
10
μA
VPG
PGOOD Low-to-High Threshold
Relative to Output Voltage Threshold
l
92
94
96
%
l
0.25
1.2
2.5
%
VPG-HYS
PGOOD Threshold Hysteresis
Relative to Output Voltage Threshold
ROL
Effective Open-Loop Output Impedance
(Note 4)
VIN = 3.6V, VOUT = 4.5V
fOSC
CLK Frequency
l
0.6
VIH
Input High Voltage
l
1.3
VIL
Input Low Voltage
l
IIH
Input High Current
l
IIL
Input Low Current
l
Ω
8
0.9
1.5
MHz
VSEL, SHDN
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliabilty and lifetime.
Note 2: Based on long-term current density limitations.
V
0.4
V
–1
1
μA
–1
1
μA
Note 3: The LTC3225 is guaranteed to meet performance specifications
from 0°C to 85°C. Specifications over the –40°C to 85°C operating
temperature range are assured by design, characterization and correlation
with statistical process controls.
Note 4: Output not in regulation;
ROL ≡ (2 • VIN – VOUT)/IOUT
TYPICAL PERFORMANCE CHARACTERISTICS
(TA = 25°C, CFLY = 1μF, CIN = 2.2μF, CTOP = CBOT , unless otherwise specified)
IOUT vs RPROG
IOUT vs VOUT (RPROG = 12k)
160
VIN = 3.6V
VOUT = 4.5V
140
100
160
90
80
140
120
80
60
EFFICIENCY (%)
100
100
80
60
40
0
0
10
20
30
40
RPROG (kΩ)
50
60
70
3225 G01
0
0
0.5
1
1.5
2 2.5 3
VOUT (V)
3.5
4
4.5
60
50
40
20
VIN = 2.8V
VIN = 3.6V
VIN = 5.5V
20
VSEL = 0
30
CTOP = CBOT
40
20
VSEL = VIN
70
120
IOUT (mA)
IOUT (mA)
Efficiency vs VIN
180
10
0
5
3225 G02
ILOAD = 100mA
CTOP = CBOT
2.5
3
3.5
4
VIN (V)
4.5
5
5.5
3525 G03
3225f
3
LTC3225
TYPICAL PERFORMANCE CHARACTERISTICS
(TA = 25°C, CFLY = 1μF, CIN = 2.2μF, CTOP = CBOT , unless otherwise specified)
30
VIN = 3.6V
VOUT = 4.5V
6
9
5
EXTRA IIN (mA)
10
IIN (μA)
4
3
25
TA = 85°C
8
20
TA = 25°C
7
TA = –40°C
6
ROL (Ω)
7
Charge Pump Open-Loop Output
Resistance vs Temperature
(2VIN – VCOUT)/IOUT
No-Load Input Current vs
Supply Voltage
Extra Input Current vs Output
Current (IVIN – 2 • IOUT)
15
10
2
1
5
0
0
VIN = 3.6V
VOUT = 4.5V
5
4
3
2
1
0
20
60 80 100 120 140 160
IOUT (mA)
40
2.5
3
3.5
4
VIN (V)
4.5
5
5.5
Oscillator Frequency vs
Supply Voltage
FREQUENCY (MHz)
85
SHDN
5V/DIV
VIN
20mV/DIV
IVIN
300mA/DIV
IVIN
200mA/DIV
VCOUT
2V/DIV
0mA
TA = –40°C
0.91
TA = 85°C
RPROG = 12k
0.90
60
3225 G08
Input Ripple and Input Current
TA = 25°C
35
10
TEMPERATURE (°C)
Charging Profile with Unequal
Initial Output Capacitor Voltage
(Initial VTOP = 1.3V, VBOT = 1V)
0.94
0.93
–15
3225 G05
3225 G04
0.92
0
–40
200ns/DIV
3225 G06
VTOP-VBOT
500mV/DIV
2s/DIV
VSEL = VIN
RPROG = 12k
CTOP = CBOT = 1.1F
0.89
3225 G09
0.88
2.5
3
3.5
4
VIN (V)
4.5
5
5.5
3225 G07
Charging Profile with Unequal
Initial Output Capacitor Voltage
(Initial VTOP = 1V, VBOT = 1.3V)
Charging Profile with 30%
Mismatch in Output Capacitance
(CTOP > CBOT)
Charging Profile with 30%
Mismatch in Output Capacitance
(CTOP < CBOT)
SHDN
5V/DIV
SHDN
5V/DIV
SHDN
5V/DIV
IVIN
300mA/DIV
IVIN
300mA/DIV
IVIN
300mA/DIV
VCOUT
2V/DIV
VCOUT
2V/DIV
VCOUT
2V/DIV
VTOP-VBOT
200mV/DIV
VTOP-VBOT
200mV/DIV
VTOP-VBOT
500mV/DIV
2s/DIV
VSEL = VIN
RPROG = 12k
CTOP = CBOT = 1.1F
3225 G10
5s/DIV
VSEL = VIN
RPROG = 12k
CTOP = 1.43F
CBOT = 1.1F
CTOP INITIAL VOLTAGE = 0V
CBOT INITIAL VOLTAGE = 0V
3225 G11
5s/DIV
VSEL = VIN
RPROG = 12k
CTOP = 1.1F
CBOT = 1.43F
CTOP INITIAL VOLTAGE = 0V
CBOT INITIAL VOLTAGE = 0V
3225 G12
3225f
4
LTC3225
PIN FUNCTIONS
C+ (Pin 1): Flying Capacitor Positive Terminal. A 1μF X5R
or X7R ceramic capacitor should be connected from C+
to C–.
VSEL (Pin 6): Output Voltage Selection Input. A logic low
at VSEL sets the regulated COUT to 4.8V; a logic high sets
the regulated COUT to 5.3V. Do not float the VSEL pin.
C– (Pin 2): Flying Capacitor Negative Terminal.
PROG (Pin 7): Charging Current Programming Pin. A resistor connected between this pin and GND sets the charging
current. (See Applications Information section).
CX (Pin 3): Midpoint of Two Series Supercapacitors. This
pin voltage is monitored and forced to track COUT (CX =
COUT/2) during charging to achieve voltage balancing of
the top and bottom supercapacitors.
GND (Pin 8): Charge Pump Ground. This pin should be
connected directly to a low impedance ground plane.
SHDN (Pin 4): Active Low Shutdown Input. A low on SHDN
puts the LTC3225 in low current shutdown mode. Do not
float the SHDN pin.
VIN (Pin 9): Power Supply for the LTC3225. VIN should
be bypassed to GND with a low ESR ceramic capacitor of
more than 2.2μF.
PGOOD (Pin 5): Open-Drain Output Status Indicator. Upon
start-up, this open-drain pin remains low until the output
voltage, VOUT, is within 6% (typical) of its final value. Once
VOUT is valid, PGOOD becomes Hi-Z. If VOUT falls 7.2%
(typical) below its correct regulation level, PGOOD is
pulled low. PGOOD may be pulled up through an external
resistor to an appropriate reference level. This pin is Hi-Z
in shutdown mode.
COUT (Pin 10): Charge Pump Output Pin. Connect COUT
to the top plate of the top supercapacitor. COUT provides
charge current to the supercapacitors and regulates the
final voltage to 4.8V/5.3V.
Exposed Pad (Pin 11): This pad must be soldered to
a low impedance ground plane for optimum thermal
performance.
3225f
5
LTC3225
SIMPLIFIED BLOCK DIAGRAM
CFLY
9
1
2
C+
VIN
4
C–
VIN
SHDN
SOFT-START AND
SHUTDOWN CONTROL
UVLO
THERMAL
PROTECTION
3000i
POR
1.2V
COUT
CX
CHARGE
PUMP
RUN
CTOP
3
CBOT
GND
8
i
7
10
PROG
CLK
RPROG
RUN/STOP
R1
OSCILLATOR
–
C1
R2
+
VREF – 2%
1.2V
POR
PGOOD
VREF
+
1.088V
6
VSEL
VREF – 6%
VREF – 7.2%
5
C2
–
3225 F01
Figure 1
3225f
6
LTC3225
OPERATION
The LTC3225 is a dual cell supercapacitor charger. Its
unique topology maintains a constant output voltage with
programmable charging current. Its ability to maintain
equal voltages on both cells while charging protects the
supercapacitors from damage that is possible with other
charging methods, without the use of external balancing
resistors. The LTC3225 includes an internal switched
capacitor charge pump to boost VIN to a regulated output
voltage. A unique architecture maintains relatively constant
input current for the lowest possible input noise. The basic
charger circuit requires only three external components.
ICOUT =
1
•I
2 VIN
If the leakage currents or capacitances of the two supercapacitors are mismatched enough that varying the
charging current is not sufficient to balance their voltages, the LTC3225 stops charging the capacitor with the
higher voltage until they are again balanced. This feature
protects either capacitor from experiencing an overvoltage
condition.
Shutdown Mode
Normal Charge Cycle
Operation begins when the SHDN pin is pulled above 1.3V.
The COUT pin voltage is sensed and compared with a preset
voltage threshold using an internal resistor divider and
a comparator. The preset voltage threshold is 4.8V/5.3V
selectable with the VSEL pin. If the voltage at the COUT pin
is lower than the preset voltage threshold, the oscillator is
enabled. The oscillator operates at a typical frequency of
0.9MHz. When the oscillator is enabled, the charge pump
operates charging up COUT. The input current drawn by the
internal charge pump ramps up at approximately 20mA/μs
each time the charge pump starts up from shutdown.
Once the output voltage is charged to the preset voltage
threshold, the part shuts down the internal charge pump and
enters into a low current state. In this state, the LTC3225
consumes only about 20μA from the input supply. The
current drawn from COUT is approximately 2μA.
Asserting SHDN low causes the LTC3225 to enter shutdown mode. When the charge pump is first disabled, the
LTC3225 draws approximately 1μA of supply current from
VIN and COUT. After VOUT is discharged to 0V, the current
from VIN drops to less than 1μA. With SHDN connected
to VIN, the output sinks less than 1μA when the input supply is removed. Since the SHDN pin is a high impedance
CMOS input, it should never be allowed to float.
Output Status Indicator (PGOOD)
During shutdown, the PGOOD pin is high impedance. When
the charge cycle starts, an internal N-channel MOSFET
pulls the PGOOD pin to ground. When the output voltage,
VOUT, is within 6% (typical) of its final value, the PGOOD
pin becomes high impedance, but charge current continues
to flow until VOUT crosses the charge termination voltage.
When VOUT drops 7% below the charge termination voltage, the PGOOD pin again pulls low.
Automatic Cell Balancing
The LTC3225 constantly monitors the voltage across both
supercapacitors while charging. When the voltage across
the supercapacitors is equal, both capacitors are charged
with equal currents. If the voltage across one supercapacitor
is lower than the other, the lower supercapacitor’s charge
current is increased and the higher supercapacitor’s charge
current is decreased. The greater the difference between
the supercapacitor voltages, the greater the difference
in charge current per capacitor. The charge currents can
increase or decrease as much as 50% to balance the voltage across the supercapacitors. When the cell voltages
are balanced, the supercapacitors are charged at a rate
of approximately:
Current Limit/Thermal Protection
The LTC3225 has built-in current limit as well as overtemperature protection. If the PROG pin is shorted to ground,
a protection circuit automatically shuts off the internal
charge pump. At higher temperatures, or if the input
voltage is high enough to cause excessive self-heating
of the part, the thermal shutdown circuitry shuts down
the charge pump once the junction temperature exceeds
approximately 150°C. It will enable the charge pump once
the junction temperature drops back to approximately
135°C. The LTC3225 is able to cycle in and out of thermal
shutdown indefinitely without latch-up or damage until the
overcurrent condition is removed.
3225f
7
LTC3225
APPLICATIONS INFORMATION
Programming Charge Current
The charging current is programmed with a single resistor
connecting the PROG pin to ground. The program resistor
and the input/output charge currents are calculated using
the following equations:
IVIN =
3600 V
RPROG
IOUT =
IVIN
(with matched outp
put capacitors)
2
An RPROG resistor value of 2k or less (i.e., short circuit)
causes the LTC3225 to enter overcurrent shutdown mode.
This mode prevents damage to the part by shutting down
the internal charge pump.
Power Efficiency
The power efficiency (η) of the LTC3225 is similar to that
of a linear regulator with an effective input voltage of twice
the actual input voltage. In an ideal regulating voltage
doubler the power efficiency is given by:
η2xIDEAL =
POUT VOUT • IOUT VOUT
=
=
PIN
VIN • 2IOUT 2VIN
At moderate to high output power the switching losses
and quiescent current of the LTC3225 are negligible and
the above expression is valid. For example, with VIN = 3.6V,
IOUT = 100mA and VOUT regulated to 5.3V, the measured
efficiency is 71.2% which is in close agreement with the
theoretical 73.6% calculation.
Effective Open-Loop Output Resistance (ROL)
The effective open-loop output resistance (ROL) of a charge
pump is an important parameter that describes the strength
of the charge pump. The value of this parameter depends
on many factors including the oscillator frequency (fOSC),
value of the flying capacitor (CFLY), the non-overlap time,
the internal switch resistances (RS) and the ESR of the
external capacitors.
Output Voltage Programming
The LTC3225 has a VSEL input pin that allows the user to
set the output threshold voltage to either 4.8V or 5.3V by
forcing a low or high at the VSEL pin respectively.
Charging Time Estimation
The estimated charging time when the initial voltage
across the two output supercapacitors is equal is given
by the equation:
t CHRG =
(
COUT • VCOUT – VINI
)
IOUT
where COUT is the series output capacitance, VCOUT is the
voltage threshold set by the VSEL pin, VINI is the initial
voltage at the COUT pin and IOUT is the output charging
current given by:
IOUT =
1800 V
RPROG
When the charging process starts with unequal initial
voltages across the output supercapacitors, only the capacitor with the lower voltage level is charged; the other
capacitor is not charged until the voltages equalize. This
extends the charging time slightly. Under the worst-case
condition, whereby one capacitor is fully depleted while
the other remains fully charged due to significant leakage
current mismatch, the charging time is about 1.5 times
longer than normal.
Thermal Management
For higher input voltages and maximum output current,
there can be substantial power dissipation in the LTC3225.
If the junction temperature increases above approximately
3225f
8
LTC3225
APPLICATIONS INFORMATION
150°C, the thermal shutdown circuitry automatically
deactivates the output. To reduce the maximum junction
temperature, a good thermal connection to the PC board
is recommended. Connecting the GND pin (Pin 8) and the
Exposed Pad (Pin 11) of the DFN package to a ground
plane under the device on two layers of the PC board
can reduce the thermal resistance of the package and PC
board considerably.
VIN Capacitor Selection
The type and value of CIN controls the amount of ripple
present at the input pin (VIN). To reduce noise and ripple,
it is recommended that low equivalent series resistance
(ESR) multilayer ceramic chip capacitors (MLCCs) be
used for CIN. Tantalum and aluminum capacitors are not
recommended because of their high ESR.
The input current to the LTC3225 is relatively constant during both the input charging phase and the output charging
phase but drops to zero during the clock non-overlap times.
Since the non-overlap time is small (~40ns) these missing
“notches” result in only a small perturbation on the input
power supply line. Note that a higher ESR capacitor, such
as a tantalum, results in higher input noise. Therefore,
ceramic capacitors are recommended for their exceptional
ESR performance. Further input noise reduction can be
achieved by powering the LTC3225 through a very small
series inductor as shown in Figure 2.
A 10nH inductor will reject the fast current notches,
thereby presenting a nearly constant current load to the
input power supply. For economy, the 10nH inductor can
be fabricated on the PC board with about 1cm (0.4") of
PC board trace.
Flying Capacitor Selection
Warning: Polarized capacitors such as tantalum or aluminum should never be used for the flying capacitor since
its voltage can reverse upon start-up of the LTC3225.
Low ESR ceramic capacitors should always be used for
the flying capacitor.
The flying capacitor controls the strength of the charge
pump. In order to achieve the rated output current, it is
necessary to use at least 0.6μF of capacitance for the
flying capacitor.
The effective capacitance of a ceramic capacitor varies with
temperature and voltage in a manner primarily determined
by its formulation. For example, a capacitor made of X5R
or X7R material retains most of its capacitance from
–40°C to 85°C whereas a Z5U or Y5V type capacitor loses
considerable capacitance over that range. X5R, Z5U and
Y5V capacitors may also have a poor voltage coefficient
causing them to lose 60% or more of their capacitance
when the rated voltage is applied. Therefore, when comparing different capacitors, it is often more appropriate to
compare the amount of achievable capacitance for a given
case size rather than comparing the specified capacitance
value. For example, over rated voltage and temperature
conditions, a 4.7μF 10V Y5V ceramic capacitor in a 0805
case may not provide any more capacitance than a 1μF 10V
X5R or X7R capacitor available in the same 0805 case. In
fact, over bias and temperature range, the 1μF 10V X5R
or X7R provides more capacitance than the 4.7μF 10V
Y5V capacitor. The capacitor manufacturer’s data sheet
should be consulted to determine what value of capacitor
is needed to ensure minimum capacitance values are met
over operating temperature and bias voltage.
10nH
9
VIN
0.1μF
2.2μF
8, 11
VIN
LTC3225
GND
3225 F02
Figure 2. 10nH Inductor Used for Input Noise Reduction
3225f
9
LTC3225
APPLICATIONS INFORMATION
The voltages on the flying capacitor pins C+ and C– have
very fast rise and fall times. The high dv/dt values on
these pins can cause energy to capacitively couple to
adjacent printed circuit board traces. Magnetic fields can
also be generated if the flying capacitors are far from the
part (i.e. the loop area is large). To prevent capacitive
energy transfer, a Faraday shield may be used. This is a
grounded PC trace between the sensitive node and the
LTC3225 pins. For a high quality AC ground it should be
returned to a solid ground plane that extends all the way
to the LTC3225.
Table 1 contains a list of ceramic capacitor manufacturers
and how to contact them.
Table 1. Capacitor Manufacturers
AVX
www.avxcorp.com
Kemet
www.kemet.com
Murata
www.murata.com
Taiyo Yuden
www.t-yuden.com
Vishay
www.vishay.com
TDK
www.component.tdk.com
Layout Considerations
Table 2. Supercapacitor Manufacturers
Due to the high switching frequency and high transient
currents produced by the LTC3225, careful board layout is
necessary for optimum performance. An unbroken ground
plane and short connections to all the external capacitors
improves performance and ensures proper regulation
under all conditions.
CAP-XX
www.cap-xx.com
NESS CAP
www.nesscap.com
Maxwell
www.maxwell.com
Bussmann
www.cooperbussmann.com
AVX
www.avx.com
TYPICAL APPLICATION
5V Supercapacitor Backup Supply
D2
7
D3
9
VIN
5V
C2
2.2μF
10V
VO
C1
1μF
10V
R3
100k
5%
PGOOD
VIN
COUT
GND
CX
8
1
2
4
5
C+
10
3
LTC3225
COUT
0.80F
5.5V
HS208F
C3
150μF
10V
C4
47μF
10V
PROG
PGOOD
VSEL
GND
7
6
10
9
R1
15k
1%
C–
SHDN
C5
0.22μF
6.3V
+
8
VIN
VO
VIN
VO
ENA
SEN
TYCO VO
AUSTIN
SUPERLYNX
TRIM
GND
GND
1
2
3
4
VO
1.8V
C7
1μF
10V
C8
1μF
10V
5
6
3225 TA02
R1
23.7k
1%
11
3225f
10
LTC3225
PACKAGE DESCRIPTION
DDB Package
10-Lead Plastic DFN (3mm × 2mm)
(Reference LTC DWG # 05-08-1722 Rev Ø)
0.64 p0.05
(2 SIDES)
0.70 p0.05
2.55 p0.05
1.15 p0.05
PACKAGE
OUTLINE
0.25 p 0.05
0.50 BSC
2.39 p0.05
(2 SIDES)
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
3.00 p0.10
(2 SIDES)
R = 0.05
TYP
R = 0.115
TYP
6
0.40 p 0.10
10
2.00 p0.10
(2 SIDES)
PIN 1 BAR
TOP MARK
(SEE NOTE 6)
0.200 REF
0.75 p0.05
0.64 p 0.05
(2 SIDES)
5
0.25 p 0.05
0 – 0.05
PIN 1
R = 0.20 OR
0.25 s 45o
CHAMFER
1
(DDB10) DFN 0905 REV Ø
0.50 BSC
2.39 p0.05
(2 SIDES)
BOTTOM VIEW—EXPOSED PAD
NOTE:
1. DRAWING CONFORMS TO VERSION (WECD-1) IN JEDEC PACKAGE OUTLINE M0-229
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE
3225f
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
11
LTC3225
TYPICAL APPLICATION
12V Supercapacitor Backup Supply
LT3740
HIGH EFFICIENCY
DOWN CONVERTER
D1
CSHD6-40C
DPAK
VIN
12V
VIN+
+
GND
C1
47μF
25V
DCAP
VOUT
LT3740
GND
VOUT
1.8V
10A
GND
GND
CHARGER 3
C2
1μF
10V
VIN
COUT
LTC3225
+
C
CX
C–
GND
10A
D2
CMSH3-20
VBIAS
3.3V
C5
10μF
M4
Si4410DY
D3
CMSH3-20
GND
C3
1μF
10V
COUT
VIN
LTC3225
C+
CX
C–
8
VM
VCC
LTC2915
7
SEL1 SEL2
3
6
TOL/MR RT
4
5
GND
RST
R7
10k
R1
2k
2
R2
100k
C6
0.1μF
M2
IRF7424
CHARGER 2
D4
CMSH3-20
1
R6
1k
1
8
PGND OUT
2 LTC4441-1 7
SGND DRVCC
3
6
VIN
IN
4
5
EN/SHDN FB
M3
Si4410DY
R3
332k
R4
84.5k
GND
R5
1k
M1
IRF7424
CHARGER 1
C7
10μF
C4
1μF
10V
COUT
VIN
LTC3225
+
C
CX
C–
GND
3225 TA03
RELATED PARTS
PART NUMBER
LTC1751-3.3/LTC1751-5
LTC1754-3.3/LTC1754-5
LTC3200
LTC3203/LTC3203B/
LTC3203B-1/LTC3203-1
LTC3204/LTC3204B-3.3/
LTC3204-5
LTC3221/LTC3221-3.3/
LTC3221-5
LTC3240-3.3/LTC3240-2.5
LT®3420/LT3420-1
LT3468/LT3468-1/
LT3468-2
LTC3484-0/LTC3484-1/
LTC3484-2
LT3485-0/LT3485-1/
LT3485-2/LT3485-3
DESCRIPTION
Micropower 5V/3.3V Doubler Charge Pumps
Micropower 5V/3.3V Doubler Charge Pumps
Constant Frequency Doubler Charge Pump
500mA Low Noise High Efficiency Dual Mode
Step-Up Charge Pumps
Low Noise Regulating Charge Pumps
COMMENTS
IQ = 20μA, Up to 100mA Output, SOT-23 Package
IQ = 13μA, Up to 50mA Output, SOT-23 Package
Low Noise, 5V Output or Adjustable
Micropower Regulated Charge Pump
Up to 60mA Output
Step-Up/Step-Down Regulated Charge Pumps
1.4A/1A Photoflash Capacitor Charger with
Automatic Top-Off
1.4A/1A/0.7A, Photoflash Capacitor Charger
Up to 150mA Output
Charges 220μF to 320V in 3.7 Seconds from 5V, VIN: 2.2V to 16V,
ISD < 1μA, 10-Lead MS Package
VIN: 2.5V to 16V, Charge Time = 4.6 Seconds for the LT3468 (0V to 320V,
100μF, VIN = 3.6V), ISD < 1μA, ThinSOTTM Package
VIN: 1.8V to 16V, Charge Time = 4.6 Seconds for the LT3484-0 (0V to 320V,
100μF, VIN = 3.6V), ISD < 1μA, 2mm × 3mm 6-Lead DFN Package
VIN: 1.8V to 10V, Charge Time = 3.7 Seconds for the LT3485-0 (0V to 320V,
100μF, VIN = 3.6V), ISD < 1μA, 3mm × 3mm 10-Lead DFN Driver
1.4A/0.7A/1A, Photoflash Capacitor Charger
1.4A/0.7A/1A/2A Photoflash Capacitor Charger
with Output Voltage Monitor and Integrated
IGBT
LT3750
Capacitor Charger Controller
ThinSOT is a trademark of Linear Technology Corporation.
VIN: 2.7V to 5.5V, 3mm × 3mm 10-Lead DFN Package
Up to 150mA (LTC3204-5), Up to 50mA (LTC3204-3.3)
Charges Any Size Capacitor, 10-Lead MS Package
3225f
12 Linear Technology Corporation
LT 0508 • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
●
www.linear.com
© LINEAR TECHNOLOGY CORPORATION 2008